Electric transformer.



' CAMPBELL.

ELECTRIC TRANSFORMER.

APPLICATION FILED MAY?. 1910.

' PatentedApr. 22, 1913.

Z SHEETS-SHEET lv fmiz C. E.. CAMPBELL. ELECTRIC TRANSFORMER.

APPLICATION wMLPD MAY?, 1910A 1,059,435, PatennedApnzawl.

Z SHEETS-SHEET 2.

. nnirnn sriirias rariiN'r ornioii.

CHARLES E. GAMHELLQE'LYNN', MassaeHUsETa-s, yassrenoa To CAMPBELL ELEC- TRIC COMPANY,

0F LYNN; MASSACHUSETTS, A CDRPOBATION 0F MASSACHUSETTS.

,c f :"nnncrnic TBANSEORMER To all whom t may concern." I

Be it known that I, CHARLES E, CAMPBELM a citizen of the United States, residing Lynn, in the county of Essex and State o' Massachusetts, have invented certain new and useful Improvements in ElectricTra/nst issue of Letters Patent, No. 1,012,326 to Charles E. Campbell on December 19, 1911.

l The object of the present invention is to produce transformers for use in electrotherapeutic apparatus having their windings so arranged that they are more efficient in operation and regulation and are more safe to use than transformers heretofore constructed. lVith the above object in View, one feature of the present invention relates to a transformer inl which certain of the primary windings are thrown in and out of circuit to regulate the primary current of the transformer.

'Another feature of the invention relates to a transformer having low-tensionand hightension secondary windings so ar :ranged that the transformer operates eiiiciently as a transformer and at the same time is protected against destructive discharges from the high-tension secondary.

Still another feature of the present invention relates to a transformer having a connection between the primary and secondary and having the primary and secondary wound in such relative circuit through the common connection and the primary and secondary series the primary and secondary windings will oppose eachother `as a rotection against accidental contact with t e primary and secondary windings.

Still other features of the present invention relate to certain constructions, arrangements and combinations of parts hereinafter described, the advantages of which will be Original application filed November 10, 1909, Serial Np. 527,153. Divided 1910. Serial N9. 560,095.

v Charles E. Campbell, No. 1,012,326.

4use a second trans rent of high frequency and of directions that in a t t circuit. The primary windings of the trans- Patented Apr. 2.2, 1913. and this application led May 7,

apparent to one skilled in the art from the following descript-ion.`

In the accompanying drawings, Figure l gis a diagram ofthe electric circuits'in an apparatus constructed in accordance with the present invention; Fig. 2 is a lanview of the apparatus with the contro ling handles, the cover-plate and other external parts removed.

The present invention is illustrated as embodied in the transformers employed in the electro-therapeutic apparatus'which is illustrated and described vin ,the patenty to The apparatus comprises as is common in apparatus of this type, a high-tension transformer adapted to be energized by alternating electric currents such as may be obtained from ordinary electric lighting systems. This transformer generates 'in its principal secondary winding an alternating current of high tension, which is converted into a suc- 'cession o f oscillatory ydischarges by means of a condenser and a spark gap. 'In combination with the high-tension transformer I I ormer or high-frequency induction coil of the type known as the Tesla coil, this second transformer or coil operating to transform the oscillatory disc arges set up y the condenser and spark gap into an alternating or oscillatory cursuch high tension as'to evince many of the characteristics of static electricity. c

In the diagram the iirst or high-tension transformer is designated generally by the reference number l and the second transformer or Tesla coil by the reference number 2. The transformer l, for reasons which will be stated hereinafter, -is of what is com monly known as the core type, having a core 'comprising two parallel legs 3 and 4 connected at their ends'by end pieces or yokes so asV to constitute a closed magnetic former are placed upon the leg 4 and constitute through which the transformer is supplied. with the alternating current by which it is i energized. After traversing the coils 5 the current passes, through a wire 8, to' the coils 6 which are wound in the same sense as the coils 5. From the coils G the current passes through a wire 9 toaseries of primary coils 10 arranged between the coils 5 and 6. Each of the coils 10 has an independent connection with one of the contact points of the primary regulator 11, and the movable contact member of the primary regulator is connected, by a wire 12, with the other supply terminal 13. The above-described arrangement of primary coils constitutes means for varying the amount of l current passing through the primary windings and energizing the transformer. When fewer turns are used in the primary winding the ratio of transformation between the secondary and primary voltages will be increased, the secondary winding being more strongly energized and forcing more current through the different external circuits connected thereto, and the primary will in consequence admit a greater primary current from the supply mains. When less energy is desired, more turns are used in the primary winding and the ratio between the secondary and the pri- -mary vvoltages is diminished, the result being that the secondary kvoltage is lessened, and'less current forced through the various secondary circuits, with consequent diminution ofV the amount of current drawn by the primary from the supply mains. The-impedance of any turn of the primary winding will bedue to its own ohmic resistance and to the magnetioflux which links said turn. The magnetic lines which link both the primar-y and the secondary and constitute the etiective flux make up one component of the total flux linking said turn of the primary, and the impedance due to this component of the flux will vary with -the impedance of the secondary circuit. Another 'component of the total' flux is the leakage flux, or the magnetic' lines linking-said turn which do not cut the secondary windings, and the impedance ldue to the' leakage lu'X is not dependent upon the impedance ofthe secondary circuit. The effective flux doesuseful work in exciting the secondary, while the leakage flux acts only to cutdown the primary current. Any primary turn is of greater efficiency the larger the ratio is between the effective and the leakage iiuX linking the turn. This greatereliiciency of some turns of the primary over others will depend upon their position upon the magnetic core with respect to the secondary coil. l have accordingly placed the coils 'and 6, which are always in circuit, at the ends of the primary le 4:' of the core, and in a position upon the magnetic circuit closest to the high potential secondary 14, giving the coils 5 and 6 the positionl of highest etiiciency. The regulating coils 10, which are not always in use, are placed on the magnetic circuit at a oscillatory discharges so as greater distance from the secondary windings tjhan the windings 5 and 6, and consequently in a position of less efficiency. The

'eect of throwing the coils 10 into the circuit will not only lessen the ratio of voltage transformation between the secondary and the primary, but the greater leakage flux of the windings 10 will cause them to act in the nature of a choke coil in the primaryv circuit and very etliciently act to controll the amount of energy drawn from the supply mains. By moving the primary regulator so as t0 include more or less of the primary coil 10 the turns of the primary winding, and thus its impedance, may be increased ordiminvished so as to vary the amount of current flowing through the primary winding.

The main secondary winding 14 of the transformer is mounted upon the leg 8 of the coreand is connected, by wires 15 and 16 with the spark gap 17.

The primary winding consists of a comparatively few turns of wire and the secondary winding of a greater number of turns, so that the transformer acts as a step-up transformer to step up the primary voltage toa high secondary tension. BV placing the primary and secondary windings upon different legs ofthe transformer core, they are more completely separated and better insulated from each other to gua-rd against possible break-down between the primary and secondary.

, A condenser 18 is connected with the wire 1G by a wire Q2, at one terminal, and the other terminal of the condenser is connected, by a wire 19, with the primary winding'QO of the Tesla coil. The winding 20 is connectedat its other terminal, by a'wire 21, with the other side of the spark gap 17 By this arrangementI the condenser is alternately charged winding Q() of the Tesla coil, and the dis- -charges have the oscillatory character duc ,to the use of the condenser and the spark crap,

b ln order to vary the frequency of the to modify the character of the currents produced by the Tesla coil, the condenser is arranged to have a variable capacity which is regulated by means of a frequency-regulator 23, as described and illustrated in the above mentioned Campbell patent. The terminals of the secondary winding '24 of the Tesla coil are connected, by conductors 25 and 26, with the vmembers of a s aark Ua a 27 which is adn l a .justablel in the ordinary manner, by means of a sliding rod`28.

ln place of connecting the primary and secondary Awindings of the Tesla coil with the earth inthe usual manner, the lowermost plate 29 of the condenser 18 is connected, by a wire 30, with the wire 12 connected with the primary winding of the and dischargedthrough the which the apparatus is energized to form a safety connection, as described in the above mentioned: Campbell patent.

Currents of the characters usually employed in therapeutics and derived from a high-frequency coil are derived` from the Tesla coil 2 in the present invention, either from the terminals of the spark gap 27 or b other connectionsillustrated in Fig. l. current of the character usually designated as a DArrson'val current is obtained thro-ugh terminals connected, by wires 32, 33 and 26, with a portion of the secondary winding 24. This portion 'is made of heavier wire than the rest of the secondary winding, and the arrangement is such that the DArsonval current supplied in this manner is of lower' tension but greater volume than the current generated in the Tesla secondary as a whole. A current of high frequency but of lower tension than that produced in the secondary winding 24 is obtained through terminals connected by wires 34 and 35 withthe ter` minals of the primary winding 2O of the.

Tesla coil. This current may bedesignated -as a thermo-faradic current.

In addition to the high-tension and highfrequency currents Aabove referred to, the apparatus is arranged to supplyalternating currents of comparatively low tension and of the frequency of the alternating current by which' thev apparatus is energized. One of these currents, which may-be designated as a sinusoidal current, and which is designed for direct personal application, is induced in an auxiliary secondary winding 36 inthe transformer l, and this secondary winding, for reasons which will be' hereinafter pointed out, ist located upon the same vleg of the core as the primary winding of the transformer and is interposed between the coils of the primarywinding. i The sinusoidal current is obtained from terminals connected, by wires 37 and. 38, with the terminals of the winding 36. i

In addition to the currents above described for direct application, the apparatus is designed to furnish currents for indirect use, such currents being adapted fory the operation 0f cauterizing apparatusand diagnostic lamps. The current for the diagnosticlamp` is. obtained from terminals which are connected, through wires38, 39A

and 40, and through a variable resistance device 4l, with the secondary winding 36.

' Thepconnections-are arranged as shown in Fig. l so that in theproduction of this current only a portion of the winding- 36'is employed',- so that the lamp current is of lower tension thanA the sinusoidal current. The variable resistance device41 constitutes a regulator for the diagnostic lamp. The cautery current is obtained Vfrom another auXiliary secondarywinding, 42, ar-

ranged adjacent to the winding 36. This winding 42`is so proportioned as to produce a current of very low tension, which may be safely used for the purpose designated. The cautery current is obtained from terminals connected with the winding 42 by means of wires 43 and 44.

To furnish at all timesl an indication when 2, the primary windings 5 and 6 each constitute two separately-wound coils. Owing to this arrangement and to the further divisionof the primary winding into 'the separarely-wound coils l0, the entire primary 4winding of the transformer is divided into a lar e number of small sections. The utility o this arrangement results from the production' in high-frequency apparatus of static currents and waves of very high tension and of incidental character which have a serious tendency to escape from the circuits of the apparatus and to leap considerable airspaces .in preference to following conductors of high impedance. Such waves or currents occur in primary winding of the transformer and ithas been found that in the absence of special precaution there is danger of the disruptive dischargev of such currents through the primary and the consequent breaking down of the insulation therein, leading to the production of destructive arcs. I have found, however, that by winding the primary in separate coils or sections as above described, the insulation of the primary winding is soimproved as toprotect it against the effects'which I have described.`

4, The arrangement of the primary winding of the transformer is such that the intermediate coils l0, when they are not included in the primary circuit tend to act as secondary coils with relation. to the main coils 5 and 6 precisely after the manner ofv an auto-transformer, that is to say, a potential in the coils 10 is induced by the magnet-ic uX in the core due to the action of the `coils 5 and 6. This potential is opposite to 1 that of the alternating current by which the primary winding is energized, and when the coils '10 are not connected 1n series with the main coils the difference in potential be.

tween the left-hand coil 10 and the adjacent right-hand coil 5 is much higher than any difference potential due to the energizing current alone. To guard against evil effects from this circumstance, a plate 46of insulating material is interposedbetween the coils 5 and the coils 10.

The control of the transformer by varying the amount of primary winding in operation is. an economical method, since the iow of current `is controlled not by waste of current in external heat-producing resistance `devices, suchv as are commonly` used,l but by the impedance in the primary winding itself. The control of the transformer is thus accomplished in an economical and effective manner without the use of any additional parts except the controlling switch,

and the bulk of the apparatus is thus mini,

mized. 1 i

The general form of the transformer is in itself a protection against the action of the high-tension oscillatory currents generated, since it permits a sufficient separation of the primary and secondary windings to prevent occurrences of disruptive discharges from the secondary winding through the primary Winding. This form of transformer has thus peculiar advantages when used. in connection with a condenser and a spark gap to produce oscillatory currents of high tension, and such an arrangement is novel so far as l am informed. v

.A further'advantage resulting from the arrangement of the main primary coils 5 and G at the extremities of the leg 4 of the transformer core resides in the fact that the principal portions vof the primary winding are thus brought as close as possible to the secondary winding, so that the magnetic paths connecting the primary and secondary windings are thus of the shortest possible length vand thus efficiency and economy in the operation of the transformer are secured. This arrangement also permits the location of the primary-regulating coils l0 at a point Where their inductive'eect is slight, so that the impedance of these coils may act more effectively to regulate the production of current in the secondary winding.

The arrangement of the transformer with a plurality of independent secondary windings adapted to generate currents of different volumes and tensions permits the use of a single transformer for a Variety of purposes and thus greatly increases -the usefulness of the apparatus without correspondingly increasing its bulk or expensea In vthis. connection it will be noted that by suitably propo-rtioning the several secondary windings.I currents of any volumes and tensions within the extreme limitations of the apparatus may be secured. 1n the preferred embodiment of the invention fhave found that for the production of the cautery current a winding of very fewv turns of heavy wire adapted to give a heavy current under an E. M. F. of about three volts gives satisfactory results while restricting the voltage to such low tension as to render-it perfectly safe and convenient for use in Cauterizing apparatus. In the diagnostic lamp, I find an E. M. F. of ten volts to be sufficient, while in the sinusoidal circuit T employ an E. M F. of twenty-four volts and the winding 36 is, therefore, suitably proportioned to produce such voltages.

The position of the secondary windings 36 andaQ upon the same leg of the transformer as the primary windings is a novel feature of importance, since it secures economy in space by placing these secondary/windingsv at ay point where prima-ry windings would have a comparatively low efficiency in exciting the secondary winding 1h Moreover, by placing the secondary windings 3G and 42 upon the same leg and between the two primary coils, a good magnetic linkage is obtained between these windings andthe primary, `with la correspondingly good vefficiency of current transformation. The arrangement has a further advantage in that it removes the comparatively low-.tension secondary windings from the neighborhood of the high-tension secondary winding 14 and thereby reduces the liability of disruptive discharges in the transformer.l ,Another danger to be guarded against in the-operation ofthe apparatus resides in the l possibility of connecting applicators to one of the DArsonval terminals and one of the thermo-faradic terminals, so as to p ut the patient or the operator into circuit with the secondary windings of both the transformer and the Tesla coil. Such a result may occur, for example, by using the right hand DArsonval vterminal and the upper thermofaradic terminal in Fig. 1. To prevent danger from such a cause, the windings of the Tesla coil are so arranged and connected that in a circuit formed -as above described they oppose each other, so that the resulting E. M. F. is equal to the diHerence and not 'tween them and the two windings in series the windings oppose each other, is illustrated in connection witha transformer of the typo commonly known as the Tesla coil, it is evident that this manner of winding is equally applicable to other types of transformers.

` As a further protection to the apparatus, the parts are so proportioned and arranged that a short-circuit, either in the spark gap 17 or in the sinusoidal diagnostic lamp or cautery terminals, cannot result in burning out thi transformer. VThis is due partly to the form of the transformer in which the magnetic flux through the core is limited by suitably proportioning the end-pieces or end yokes ofthe core, and also to the use of sufficient resistance in the secondary coils 3G and 42 and of a suiiiciently small number of turns in these coils to prevent the overloading of the primary coils of the transformer.

While the various features of my invention are particularly susceptible to conjoint use in an apparatus of the kind.hereinbefore referred to, since they all contribute to the reduction of a safe and reliable apparatus, 1t will be obvious that the invention in some of its aspects may be embodied in an apparatus from which solne of the noted features are omitted. The invention hereinbefore described is not limited to the embodiment specifically illustrated and described, but may bev embodied in various other forms within the spirit of the invention and the scopeV of the following claims.

I claiml. An electric transformer having, in combination, a core having two substantially parallel legs connected by end yoles, a primary windingon one leg divided into sec- Ations located principally near the ends of the leg, a low-tension secondary winding on the same leg as the primary winding and interposed between the sections of the primary winding, and a high-tension secondary winding on the second leg of the core.

2. An electric transformer having, in combination, a core having a plurality of legs, a primary winding on one leg divided into sections located principally near the ends of leg, a low-tension secondary on the same leg as the primary'and interposed between the sections of the' primary winding, and a hightension secondary winding on another leg of the core.

3. An electric transformer having, in combination, a secondary winding, and a primarywinding consisting of a plu 1ality of sections of vwhich certain sections possess comparatively good rmagnetic linkage with the secondary and are adapted to always be in circuit when the transformer is used and of which .certain other sections possess a comparatively poorer magnetic linkage with the secondary, and means for throwing more or less of the latter named sections of the primary winding in series with the firstl named sections of the primary winding to regulate the primary current.

-l. An electric transformer having` in combination, a magnetic core having a plurality of legs, a primary winding, and a sccondanv winding on the sam'e leg as the primary winding in proximity to the prin'iarv winding having a few turns of wire of sutlicient resistance so that the overloading of the transformer is prevented in case the secondary is short-circuited.

An electric transformer having, in combination, a magnetic core of comparatively high reluctance having a plurality of legs, a primary winding, and a secondary winding on the same leg as the primary winding in proximity to the primary winding having a few turns of. wire of sufficient resistance so that the overloading of the transformer is prevented in case the secondary is shortcircuited.

(l. An electric transformer having, in combination, a primary winding, a secondary winding, and an electrical connection bctween one end of the primary winding and one end of the secondary winding, the primary and secondary windings being wound relatively to each other in such directions that in a circuit formed through said electric connection Aand the two windings in series the windings oppose each other so that the resultantI E. M. F. in said circuit is equal to the difference of the E. M. Ffs of the individual windings.

CHARLES E. CAMPBELL.

llitnesses z i HORACE VAN EVEREN, Fai-sn R. CAMPBELL. 

